Vertical cavity surface emitting laser design and method

Abstract

A microcavity pixel design and structure allowing for tuning the optical cavity length of the microcavity of a microcavity pixel structure. This is achieved by including an intermediate electrode in the device which has an overhang region to form a connecting area to a bottom electrode, alleviating design restrictions in material type and dimensions throughout the optical microcavity tuning process. A method for the fabrication of a multi-colored microcavity pixel array facilitating the use of blanket deposition methods for select layers within a microcavity pixel structure.

We claim: 
     
       1. A vertical cavity surface emitting laser (VCSEL) device comprising:
 a substrate; 
 a bottom first electrode on the substrate; 
 a first Distributed Bragg Reflector (DBR) comprising multiple layers alternating between a high refractive index material and a low refractive index material; 
 an intermediate electrode comprising an overhang region and a connecting area, the overhang region and the connecting area electrically connecting the intermediate electrode to the bottom first electrode; 
 a definition layer covering the overhang region and leaving a portion of the intermediate electrode uncovered forming an active area of the intermediate electrode; 
 a light emitting stack on top of the active area of the intermediate electrode; 
 a top electrode on top of the light emitting stack; and 
 a second Distributed Bragg Reflector (DBR) deposited on top of the top electrode. 
 
     
     
       2. The VCSEL of  claim 1 , wherein the first DBR acts as a first reflective surface and the second DBR acts as a second reflective surface to form an optical microcavity. 
     
     
       3. The VCSEL of  claim 1 , further comprising one or more of a first filler layer between the first DBR and the intermediate electrode and a second filler layer between the second DBR and the top electrode. 
     
     
       4. The VCSEL of  claim 3 , wherein a thickness of the first filler layer and a thickness of the second filler layer can be changed to provide a desired optical path length. 
     
     
       5. The VCSEL of  claim 3 , wherein the first filler layer and the second filler layer are is selected from an inorganic material and an organic material. 
     
     
       6. The VCSEL of  claim 3 , wherein the first filler layer and the second filler layer comprise one or more of indium tin oxide (ITO) and indium-doped zinc oxide (IZO). 
     
     
       7. The VCSEL of  claim 1 , wherein the intermediate electrode comprises a semi-transparent thin film metal or a transparent conductive oxide material. 
     
     
       8. The VCSEL of  claim 1 , wherein the top electrode comprises a semi-transparent material, a transparent conductive material, or a transparent material. 
     
     
       9. The VCSEL of  claim 1 , wherein the light emitting stack comprises one or more of a hole injection layer (HIL), a hole transport layer (HTL), an electron injection layer (EIL), an electron transport layer (ETL), and an emissive layer (EML). 
     
     
       10. The VCSEL of  claim 1 , wherein the bottom first electrode comprises indium tin oxide (ITO), a conducting polymer, or a layer of metal. 
     
     
       11. The VCSEL of  claim 1 , wherein the intermediate electrode is an anode. 
     
     
       12. The VCSEL of  claim 1 , wherein the definition layer comprises an inorganic material, an insulating dielectric material, or an organic material. 
     
     
       13. A method for fabrication of a vertical cavity surface emitting laser (VCSEL) device comprising:
 a substrate; 
 depositing a bottom first electrode on the substrate; 
 depositing a first Distributed Bragg Reflector (DBR) comprising multiple layers alternating between a high refractive index material and a low refractive index material on the bottom first electrode; 
 depositing an intermediate electrode above the first DBR, the intermediate electrode comprising an overhang region and a connecting area, the overhang region and the connecting area electrically connecting the intermediate electrode to the bottom first electrode; 
 depositing a definition layer covering the overhang region and leaving a portion of the intermediate electrode uncovered forming an active area of the intermediate electrode; 
 depositing a light emitting stack on top of the active area of the intermediate electrode; 
 depositing a top electrode on top of the light emitting stack; and 
 depositing a second DBR on top of the top electrode. 
 
     
     
       14. The method of  claim 13 , further comprising depositing a filler layer between the first DBR and the intermediate electrode. 
     
     
       15. The method of  claim 13 , wherein the intermediate electrode and the top electrode comprise a semi-transparent material or a transparent material. 
     
     
       16. A vertical cavity surface emitting laser (VCSEL) comprising:
 an array of vertical surface emitting laser (VCSEL) devices, each VCSEL device comprising:
 a substrate; 
 a bottom first electrode on the substrate; 
 a first Distributed Bragg Reflector (DBR) comprising multiple layers alternating between a high refractive index material and a low refractive index material; 
 an intermediate electrode comprising an overhang region and a connecting area, the overhang region and the connecting area electrically connecting the intermediate electrode to the bottom first electrode; 
 a definition layer covering the overhang region and leaving a portion of the intermediate electrode uncovered forming an active area of the intermediate electrode; 
 a light emitting stack on top of the active area of the intermediate electrode; 
 a top electrode on top of the light emitting stack; and 
 a second DBR on top of the top electrode. 
 
 
     
     
       17. The VCSEL of  claim 16 , wherein the first DBR acts as a first reflective surface and the second DBR acts as a second reflective surface to form an optical microcavity. 
     
     
       18. The VCSEL of  claim 16 , wherein the intermediate electrode is a cathode. 
     
     
       19. The VCSEL of  claim 16 , further comprising one or more of a first filler layer between the first DBR and the intermediate electrode and a second filler layer between the top electrode and the second DBR. 
     
     
       20. The VCSEL of  claim 19 , wherein changing a thickness of the first filler layer and a thickness of the second filler layer achieves a desired optical path length. 
     
     
       21. The VCSEL of  claim 16 , wherein the intermediate electrode and the top electrode comprise a semi-transparent material or a transparent material. 
     
     
       22. The VCSEL of  claim 16 , further comprising a first filler layer between the first DBR and the intermediate electrode and a second filler layer between the top electrode and the second DBR.